The invention relates generally to continuous casting.
More particularly, the invention relates to a mold for the continuous casting of metals, especially steel, and a method of making the mold.
Since the inception of continuous casting using through molds, the art has been concerned with the problem of air gap formation below the meniscus and between the strand shell and mold wall. Air gap formation substantially reduces the heat transfer between the mold and the strand shell and causes non-uniform cooling of the strand shell. This leads to defects in the strand such as rhomboidity, cracks, microstructural faults, etc. Many proposals have been made to achieve the best possible contact on all sides between the strand shell and the mold wall along the entire length of the mold, and hence the optimum conditions for heat removal. These include walking beams, injection of coolant into the air gap, mold cavities with varying tapers, and so on.
A mold for the continuous casting of steel strands having polygonal and, in particular, square cross sections is known from U.S. Pat. No. 4,207,941. The mold cavity, which is open at two ends, has a square cross section with corner concavities at the molten steel inlet end and an irregular dodecagonal cross section at the strand outlet end. The taper in the casting direction increases progressively towards the corners in the corner regions and, along part of the length of the mold, is approximately twice as large in the area of a concavity as in the central zone of the mold wall. When casting with such molds, the strand can become wedged in the mold thereby leading to cracking of the strand and breakouts. Moreover, a dodecagon is cast rather than a square. It is particularly difficult to dimension molds of this type so that the casting speed can be varied during a running casting operation as is required with long sequence casts having many ladle changes.